An old acquaintance of mine was an avid Phish fan. On More than one occasion, they would perform various cover tunes - once I was told they performed the entire "Dark Side of the Moon"

I wouldn't classify them as a tribute band, but they are often known for performing other people's music.

One of my other favorite "tributes" was in December of 1980, at the Spectrum in Philadelphia - the night after John Lennon was murdered. Bruce Springsteen walked out on stage and talked abbout John and what he meant to him, then he and the E-Street band performed an amazing tribute of Beatle and Lennon songs to start off a very memorable non-stop 4 hour concert.